The Cocktail Party Effect That Plagues Spies & Agents

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The Cocktail Party Effect That Plagues Spies & Agents

As on of the best de bugging experts in India, we are well equipped to act on your fears of someone knowing exactly what is going on in your life and then watching over you. Remember knowledge is power. Someone who is spying on you and knows every conversation of yours is privy to all your secrets and has power over your life! Similarly you could turn the tables on your enemies by being armed with information that can be used against them. And the first step begins with knowing all the information about bugs and transmitters. Some of it may be technical but knowing all this can make you well armed with basic knowledge when you talk to experts tomorrow. Also know more about the cocktail party effect later in the article!

Surveillance Transmitter’s Frequency

Let us look at a Surveillance Transmitter’s frequency. A surveillance transmitter’s frequency falls between 20 MHz and 500 MHz. ‘Baby sitters” or “wireless microphones” use the commercial FM band of 88 MHz to 108 MHz. But if your enemy has enough skill and resources, they  can use almost any RF frequency.

If your enemies are going to use a baby sitter or wireless microphone transmitter, they will probably set the operating frequency a little below 88 MHz or a little above 108 MHz by adjusting its coil. Commercial FM receivers will then have a reduced chance of picking up their transmission! Because it would be indeed weird for the old lady upstairs listening to Golden Bollywood Hits hosted by Jeetu Raj to suddenly hear you and your partner’s love making noises! Your enemies will try to pick an unused frequency. Government-allocated radio frequencies are public information, so a little research on the web will show your enemies the clean areas of the spectrum in your vicinity.

Technical Surveillance 

Technical surveillance generally uses three frequency bands. They are low band VHF, 36 to 50 MHz, high band VHF, 150 to 174 MHz; and UHF, 450 to 512 MHz. You tune a frequency by changing the mixer resonant circuits, RF amplifier and local oscillator at the same time for best results. Each frequency band has its own conditions. Low band VHF frequencies do not lose as much power when traveling far. However, they are very bad at penetrating structures. Low band VHF signals suffer skip interference and have limited area saturation. Buildings are made with steel structural members, rods for reinforcement, concrete and metal panels – all of these elements hinder radio waves. Consequently doors and windows could wind up being the only openings for radio waves in these structures. Low band VHF signals have wavelengths of 19 to 33 feet, too long to escape intact from small openings. Skip interference occurs when long-traveling signals reflect strongly from the ionosphere back to earth. Area saturation is the condition of a radio signal reflecting and re-reflecting. Low frequencies reflect less, causing dead spots and shadows.

If your enemies need to send signals where land masses block the path, they will most likely use high band VHF. This range also penetrates buildings well, but is less successful than low band VHF for line-of sight transmission. For optimum transmission through an environment filled with metal structures, they will use the UHF band. The higher the signal’s frequency, the shorter distance it can travel. High frequencies possess short wavelengths and vice versa. For long range transmission, low band VHF is good, high band VHF medium, and UHF is bad. To avoid skip interference, the best bets are UHF or high VHF, with low VHF faring not so well. Experienced bugging operators will use UHF to achieve the best area saturation, high VHF when this is of medium concern, and low VHF when it is of little concern. When the area poses a great deal of structural interference, UHF gives the signal the best passage, high VHF a medium success rate, and low VHF a negligible showing at best.

FM Transmitters Used for Bugging

Best Radio Sweeps investigators MumbaiTwo types of FM transmitters are used for bugging. The cheaper transmitter is one that is tuned to the operating frequency by an inductance /capacitance integrated circuit. It exhibits frequency drift often and is called “free running.” The free running circuit, usually a micro miniature device, transmits in various bands but the cheaper units usually live in the commercial FM band. The Indian Broadcast Commission has enacted a law which prohibits, or at least restricts, the selling of FM transmitters to unlicensed operators. Most of these “hobbyist” units are now required to be offered in kit form; the logic being that a true electronics’ hobbyist should be able to build his own unit. Several companies have edged around the kit laws by offering their units completely constructed except for the soldering of one component, usually the microphone element.

Law enforcement agents and serious surveillance folks who are employed by your enemies will more likely employ the other type, the crystal-controlled transmitter. Its quartz crystals regulate the exact the operating frequency allowing for little frequency drift. Crystal controlled units are usually a bit higher in price but for the most part, well worth the difference as they will experience fewer problems with receiving the unit’s signal.

Chances are your enemies will also think carefully about how much RF power, they need to use. While more power increases transmission range, it also renders your operation more vulnerable to eavesdropping on your eavesdropping and countermeasures. They will use the minimum amount of power necessary to get the job done. If they only need to transmit sounds from one room to another nearby room or vehicle, they can probably get by with a sub-miniature unit powered from hearing aid batteries. They will not use such a device when transmitting for hundreds of feet, or penetrating commercial buildings, despite advertising claims of viability for more than 1,000 feet. Its just not true. 

Efficiency of the Antenna

A transmitter’s range has to do with the degree of RF power as well as the efficiency of the antenna. Range, efficiency and optimal power usage decline with any design change of the antenna affecting its tuned length. Sub-miniature devices modified to fit inside cigarette packs, ash trays and shoe heels have insufficiently long antennas. Their range is quite limited, compared to what it would be if their antennas were of proper length. Your enemies also run a risk of being easily detected when using cheap commercial “wireless microphones” because of the frequency range they transmit and the amount of spurious signals called harmonics they produce.

If your enemy feel there is absolutely no danger of someone looking for the unit, or tuning across it accidentally while operating an FM receiver in the vicinity, they will use these devices, but the risk remains – anyone listening to a nearby radio may may run across the signal or the traditional feedback howl when the transmitter is operating nearby. Your enemies will give much thought and deliberate on the kind of device they require based on the power needed to receive its signals, and how much time it takes to install the unit and their budget for the job. They will determine precisely how much power they need, because the less RF power emitted, the less chance of detection. They will balance power needs with simplicity of installation. If they know that they have little access time, they will use a transmitter with its own power source and integral antenna. The time they save in simply dropping the device under a chair outweighs the drawback of radiating excess RF power.

The best method though is to still conduct an effective audio surveillance by correctly installing a modern crystal controlled transmitter along with a proper antenna. A range of at least one mile can be achieved with careful planning and the use of a sensitive receiver at the listening post.

The Cocktail Party Effect

A carelessly placed unit, i.e., tossed underneath the file cabinet or buried in a planter, will simply not overcome its poor placement to convey the necessary intelligence. Part of the problem is a something known as the “cocktail party effect”; this happens when a microphone is not located at the center of the target conversation and only transmits an unintelligible babble instead of coherent information.

At a party, your ear can selectively focus on only one conversation and filter out background chatter. The microphone you hide behind a painting or in the ceiling is not so blessed and will pick up and transmit all noise at the same level. This makes it difficult at the listening post to make sense of any the babble. To avoid this effect, your enemies will try to anticipate where your targeted conversation will take place and center the microphone there. Another thing your enemies will consider when placing the microphone is how quickly sound loses power after leaving its source. Say your friend is talking to you from 10 feet away. If you then stand 20 feet apart, the magnitude of his voice doesn’t become one-half as loud – it actually cuts to one-fourth. The magnitude of sound declines according to the inverse square law. If you quadruple the distance between you and your friend, the power of the sound of his voice drops to one-sixteenth!

The Concept of Snuggling

On a more technical note, your enemies might consider snuggling when they choose an operating frequency to record your conversations. They will set the operating frequency of the transmitter near the operating frequency of a nearby, high powered FM station like Radio City or Radio MirchiCommercial FM receivers normally lock on a strong signal and will ignore yours making the chance of discovery a bit less! Some programmable receivers will reduce the nearby station’s strength to more easily pick up your signal. Anyone performing a countermeasures sweep with a cheap RF receiver or field strength type meter will be hard pressed to discover the snuggling signal. Which is why you must hire only the best countermeasures & anti bugging experts to sweep your premises because cheap detectives operating in the business will be using cheap receivers and will give you an ok and you then you are relieved that all is fine when in fact your conversations are still being heard and recorded!

Another good idea that your enemies will use to avoid detection is to use a carrier current transmitter instead of an RF unit. Carrier current transmitters broadcast along telephone or AC electrical lines. They throw little RF into free pace because the operating frequency is between 50 KHz and 250 KHz, the very low frequency (VLF) area of the spectrum. You can conceal carrier current transmitters anywhere along AC power lines near the target. It will be hidden in appliances, wall power sockets or lamps, for example. The low frequency and negligible radiated power of carrier current transmitters are less easily detected by countermeasures receivers than transmissions broadcast through space. Battery problems disappear because energy comes from AC lines.

The “stock” carrier current transmitter – receiver combo is the Radio Shack Wireless Intercom. This unit will transmit room conversation over the wiring in a building or between buildings where the electrical wiring does not pass through a power company transformer. Carrier current units are cheap, effective, do not require batteries and are hard to find.

Contact us if you think you are being bugged. We will find out the bugs and squash them and that’s a guarantee! You can contact me on +91 98206 07875 and take an appointment for a visit to your office if you are located in Mumbai, Pune or Nashik. 

Author Bio

Amit Sen, a commercial pilot by training, has over 15 years experience in the space of corporate investigations, handling Copyright & Trademark infringement cases, Pre – employment verification Industrial Espionage investigations, Asset & Net – Worth assessment assignments and vendor / supplier verification cases, among others. Co-founder of Alliance One – who are the best de bugging and radio sweep detectives in Mumbai. Amit has also successfully completed assignments in a wide range of sectors, including the machine tools industry, pharmaceutical industry, hospitality sector, specialized equipment (Oil & natural gas sector, aviation industry etc.), telecom industry & the IT & ITes sectors. These cases have all involved both offline and online investigations.



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